1. Field of the Invention
This invention relates to computer-aided design (CAD) systems and in particular graphic symbology for graphic elements in such systems.
2. Background Information
Creating designs and managing information for buildings, civil engineering projects, transportation systems, process plans, discreet manufacturing facilities, utilities and telecommunications networks can be accomplished more readily using computer-aided design (CAD) software. Robust CAD systems used for the design and management of architecture, engineering and construction (AEC) projects employ pre-defined graphic symbology to represent each particular graphic element, which in turn, represents actual items or components within the engineering system or structure being designed. Graphic symbology referred to herein as simply “symbology” are properties used to define the graphic presentation of an element. Typical symbology properties include color, line thickness (also referred to as line weight), line style (i.e. solid, dashed, dotted, etc.). Further types of symbology properties are discussed later in this document. Some CAD systems only store symbology definitions in external files or database tables disconnected from the geometry, in those systems the combination of geometry and symbology definition is used to display a graphic element.
Clients, such as companies and governmental entities, often have standards to be followed by architects and designers so that each of the drawings for the design adhere to the same standard leading to a uniform presentation of the components and systems across the various vendors, subcontractors and designers that are involved in the project. A set of symbology properties to be followed for a particular client, project or user is referred to herein as a “graphic standard” for that project.
CAD systems typically employ user interfaces which allow an engineer or designer to manipulate lines, shapes, text and symbols which represent actual components of the system being modeled. Many CAD systems define symbology “by level”. The “by level” symbology assign common symbology properties to a level, and then any graphic elements placed on that level inherits its symbology from the level. The common symbology properties that are typically defined “by level” include color, line weight and line style. Other CAD systems, such as MicroStation, can use level as just another symbology property of a graphic element.
Symbology is an important concept in CAD since it is the way a user can discern the meaning of one graphic element from another. This makes complying with the symbology rules defined in a graphics standard critical to the project. The subsequent examples show how the level and color symbology properties can be used within a CAD drawing. Drawing levels, or layers, can be exposed or suppressed depending upon the user's selection. For example, in an architectural drawing, exterior walls can be assigned to the first level and interior walls can be assigned to the second level such that both levels can be displayed in the user interface at once or one or the other level can be displayed, allowing the user to view the external and internal walls independently. The drawing level is thus a symbology property that a graphic element will have. Thus, graphic elements that represent the same real world component may be displayed in one particular color. For example, 8″ concrete masonry unit (CMU) walls may appear in the color red, while all 12″ CMU walls may be shown in blue, according to a graphic standard for a particular architectural project. Thus, colors, like other symbology properties of graphic elements that can be used to denote different real world components.
Some CAD systems define named sets of symbology properties that include not only level, color, line weight and line style but also properties, such as, symbol name, text font, text size, hatch spacings and the like. These systems do not provide a way to associate a named set of symbology to a specific graphic element. In other words, there is no functionality in the software for explicitly linking or inferring a relationship between the graphic element and a named set of symbology properties that are defined for a particular user, a particular project, or corporate graphic standards. Furthermore, as will be understood by those skilled in the art, that there are typically no provisions for associating the same named symbology sets to graphic elements produced by different CAD systems. Because of this limitation the ability to have a quick technique for recognizing associations between graphic elements named sets of symbology properties to assist in maintaining graphics standards across the various CAD systems does not exist.
Some commercially available CAD systems employ “feature-coded” symbology which allows a particular graphic element to be tagged with a feature code which means that a particular feature is associated with such an element. This feature code is then essentially a pointer to an associated database table which contains the particular desired symbology for that type of component. However, these feature-coded designs allow one set of symbology properties per feature type. Thus, a range for one or more of the symbology properties cannot be specified using feature-coding. In addition, in feature coded systems since the definitions are external to the file containing the graphic elements there is no direct relationship between a symbology definition and a feature coded graphic element.
As noted, many CAD systems operate in conjunction with an associated database which contains all of the information about the attributes of the physical components of the system and the graphic symbology properties that are associated with each such attribute of the physical components. As this information is available only in the associated database this means that this database must be accessible in order to utilize the information. Thus, in a GIS environment or when a handheld PDA is being used in the field, where direct connections or even wireless service is not available, there may not be a way to connect to the database and thus the symbology information in the database is not accessible by that program.
Furthermore, even if the CAD system does have access to the database, and includes the feature coding function each graphic element is typically tied to a particular set of valid symbologies. Thus, a range or choice of symbologies is not typically available to the user through the commercially available user interfaces. Symbology definitions for graphic elements typically can not be managed at the property level in such systems. This limitation inhibits the ability of the CAD system to check graphic elements for compliance with an applicable graphic standard and allow non-compliant graphics to be corrected.
There remains a need therefore, for a system that can be used with a CAD software platform that allows a relationship to be persisted between a graphic element and a named set of graphic symbology properties that adhere to a defined graphic standard. There remains a further need for such a technology which provides a flexible way to configure the set of files that define these graphic standards so that these files can be protected, yet can be easily edited when changes are desired. There remains yet a further need for a technology that allows CAD users to easily create graphics that comply with properties defined in graphic standards, check existing drawings for compliance, and allow for correction of elements that are not compliant.